Tanner Conroyd left her house on Route 31 in unincorporated Kane County near St. Charles on Sunday after an argument with family members, according to the Kane County sheriff's office. Her father believed she was on her way to Illinois State University in Normal, where she was planning on attending the fall semester although she had not yet enrolled as a student.

Her family called friends in Normal and when they hadn't heard from Conroyd reported her missing Sunday night to the Normal Police Department, which began an investigation with help from the Kane County sheriff and the St. Charles, Sugar Grove and Chicago police departments.

A preliminary police investigation determined she left her home about noon Sunday and got gas at a Sugar Grove station about 1 p.m., then at about 1:30 p.m. was seen at the Brown Pub in Hinkley.

Conroyd stayed there about three hours, and it is believed she had car trouble. She solicited the help of an area resident who gave her a ride to the Aurora Transportation Center, where it is believed she took a train to Union Station in Chicago, the sheriff's office said.

She was next seen in Millennium Park, and as it was closing about 10:30 p.m. Sunday she spoke with a security guard there and gave him her cell phone number -- telling him he could call to make sure she got home OK.

But when he called later the guard reached Conroyd's family at home, where she had left the phone, police said. The last confirmed sighting of Conroyd was Monday, again in Millennium Park.

The missing person alert describes Conroyd as a white woman, 5-foot-6 and about 160 pounds, with brown hair and green eyes.

She was wearing a pink shirt and blue Capri pants, and gold-framed glasses. She is believed to be carrying a red guitar, possibly in a black soft-sided case.

Her car, a white 1995 Ford Crown Victoria, was located as part of the investigation Wednesday near the Brown Pub in Hinkley, where it was believed to have been since Sunday.

The woman's family says her behavior is unusual and she might be suffering a psychological issue. They believe she might be near a park, library, anything related to music, a museum or a college campus. They have started a Facebook page called Find Tanner Conroyd, police said.

The sheriff's office has not ruled out foul play in Conroyd's going missing, although detectives continue to interview people and things could change as the investigation goes on, according to Kane County officials.

Anyone with information is asked to call Kane County sheriff's detectives at 630-444-1103.